Lining for underground excavations

ABSTRACT

A lining for underground excavations comprises a floor base, a shield, a roof cap for supporting the mine roof, a pit prop for engaging the floor base and the shield and pushing the roof cap into abutment with the mine roof, and a support assembly for displacing a lower end of the shield along an arcuate path and fixing it in a plurality of positions along this path.

United States Patent 91 Spies Dec. 17, 1974 1 LINING FOR UNDERGROUND EXCAVATIONS [75] Inventor: Klaus Spies,

Dortmund-Wellinghofen, Germany [73] Assignee: Bochumer Eisenhutte Heintzmann &

Co., Bochum, Germany [22] Filed: May 18, 1973 [21] App]. No.: 361,643

[30] Foreign Application Priority Data May 18, 1972 Germany 2224207 [52] US. Cl 61/45 D [51] Int. Cl E2ld 15/44 [58] Field of Search 61/45 D; 299/31, 32, 33;

[56] References Cited UNITED STATES PATENTS 2,566,003 8/1951 Vogel 299/32 2,781,888 2/1957 Lobbe 198/126 X FOREIGN PATENTS OR APPLICATIONS 1,503,990 10/1967 France 61/45 D 1,934,376 3/1970 Germany 61/45 D 156,132 l/l964 U.S.S.R..... 61/45 D 243.551 2/1970 U.S.S.R 61/45 D Primary ExaminerDennis L. Taylor Attorney, Agent, or FirmMichael S. Striker [5 7 ABSTRACT 15 Claims, 4 Drawing Figures LINING FOR UNDERGROUND EXCAVATIONS BACKGROUND OF THE INVENTION The invention relates to a lining for underground excavations particularly of the type which comprises a floor base, a shield attached to and extending over the same, a roof cap supported by the shield and projecting beyond the same for supporting the roof of the excavation, and at least one adjustable pit prop engaging the shield or the roof for pushing the same against the roof.

In the conventional linings of this kind, the shield is attached to the floor base by means of a pivot, and the shield is rotatable about this pivot in relation to the floor base. The purpose of this arrangement is to ensure a proper functioning of the lining regardless of the thickness of the seam being exploited. However, such an arrangement is disadvantageous in that the free end of the shield and, consequently, the roof cap follow a circular path centered on the axis of said pivot while being adjusted to accommodate it to various distances between the floor and the roof of the excavation. This, in turn, results in different distances between the end of the roof cap and the mine face for different seam thickness. However, it is necessary to keep this distance to a minimum in order to ensure optimum control of the roof of the excavation.

It is already known to avoid this drawback by making the shield extendable and/or by resetting the roof cap in relation to the free end of the shield. However, even these measures are unsatisfactory, since the adjustment means of the shield and of the roof cap are located in those regions of the lining which are subjected to maximum forces and moments. Furthermore, the provision of the structurally relatively weak adjustment means in these regions either results in a considerable weakening of the structure of the lining in these regions or, on the other hand, the adjustment means of the shield and of the roof cap must have a sturdy construction which contributes to increased cost of the lining. Moreover, the superimposition of the circular rotation of the shield on the linear movements resulting from the extension of the shield and/or the resetting of the roof cap does not represent an advantageous geometric solution of the problem of assuring the minimum distance between the end of the roof cap projecting beyond the shield and the mine face under all operating conditions.

SUMMARY OF THE INVENTION It is an object of the present invention to avoid the disadvantages of the heretofore known linings.

It is a particular object of the present application to provide a lining for underground excavations in which the distance between the projecting end of the mine cap and the mine face is kept to a minimum under all operating conditions and regardless of the thickness of the seam, without resorting to utilization of shield extension means and cap resetting means.

A concomitant object of the invention is to provide a lining for underground excavations which assures a reliable support of the mine roof regardless of the distance between the mine floor and the mine roof.

ln pursuance of the above objects and others which will become apparent hereinafter, one feature of the present invention resides in the provision of a support assembly for adjustably connecting the floor base and one end of the shield so as to enable the one end of said shield to move along an arcuate path in relation to the floor base and to be fixed in one of a plurality of positions along the path. In a currently preferred embodiment of the invention, the support assembly is pivotably attached to one side of the floor base, and a pivot, about which the shield is journalled, is supported in said support assembly so as to follow an arcuate path whose distance from the floor base increases as the pivot moves from the one side of the floor base in direction toward the other side thereof. In this manner it is achieved in a relatively simple way that the projecting end of the roof cap supports the mine roof in the immediate vicinity of the mine face under all operating conditions and regardless of the instantaneous thickness of the seam being exploited, without incurring the extra expenses and accepting the desing drawbacks of the conventional linings using extendable shields and/or resettable roof caps.

In an advantageous embodiment of the invention, the adjustable support assembly comprises a support which is pivotably connected to the one side of the floor base so as to rotate in relation to the floor base, and an adjusting device by which the support may be fixed in one of a plurality of positions within its range of movement. Preferably, the support is constructed as a support plate whose dimension in the direction perpendicular to the rotation of the support plate substantially equals the dimensions of the floor base and the shield in the same direction.

The adjusting device advantageously comprises at least one adjusting lever pivotably attached to the one side of the floor base and provided with a plurality of recesses which are mutually spaced in the longitudinal direction of the adjusting lever and which serve for accommodation of an arresting member associated with the pivotable support. In an advantageous embodiment, the recesses are shaped as holes and the arresting member is a detent inserted into the holes in the support and into one of the holes of the adjusting lever. In another advantageous embodiment, the recesses are open in direction toward the support and the detent is accommodated in the support and in one of the open recesses of the adjusting lever. If such is the case, experience has shown that it is advantageous to provide the adjusting levers with means for accommodation of at least one self-locking key in the region of the open end of each of the recesses, the self-locking key serving for securing the detent in the particular recess.

If the pivotable support is constructed as a support plate in accordance with the currently preferred embodiment of the invention, then the support plate is provided with recesses or openings for accommodation therein of preferably two adjusting levers which are rotatably attached to the one end of the floor base, and for engagement therewith in a plurality of positions.

The range of movement and adjustment of the support or the support plate preferably extends from a position in which the support encloses an acute angle of 30 with the one side of the floor base, to a position in which the support is perpendicular to the floor base, and the support may be fixed in a plurality of positions within this range.

In general, it is sufficient if the pivotable support or support plate is attached to the floor base by means of a pivot which is stationary in relation to the floor base,

in such a manner that the pivot, about which the shield is journalled and which is supported in the support at the end of the latter which is opposite to the end at which the support is attached to the floor base, follows a circular path whose center coincides with the axis of the pivot which connects the support to the floor base, so that the distance between the pivot supporting the shield and the floor base increases as the support moves from the one side of the floor base toward the other side thereof within its range of movement and adjustment.

In a yet more preferable embodiment of the invention which solves the problem of adjustment of the lining to the different seam thickness in an even more satisfactory manner, the pivot connection of the support or the support plate is constructed so that the end of the support, which is opposite to the end at which the support engages the floor base, moves along an arcuate path whose slope is larger than that corresponding to the circular movement of the respective end and thus the pivot about which the shield is joumalled.

This advantageous solution can be accomplished in a relatively simple manner by accommodating the pivot which connects the shield to the floor base in a cam opening of a bracket rigidly attached to the floor base, and by providing the support or support plate with a cylindrical end whose axis does not coincide with the axis of the pivot and which abuts against the floor base, so as to support the support plate on the same in such a manner that the support or the support plate, or the pivot about which the support rotates, is gradually lifted while the support plate rotates in the direction from the one toward the other side of the floor base. When using such an arrangement, it is ensured that the shield and the roof cap which is supported in the free end of the shield can be perfectly adjusted to the distance between the mine floor and the mine roof so that the distance between the projecting end of the roof cap and the mine face is kept to a minimum under all operating conditions.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a cross-section of an underground excavation with a lining according to the invention shown in a side elevation;

FIG. 2 shows an enlarged cross-section taken on the line II-Il of FIG. 1;

FIG. 3 shows a different embodiment of a support assembly to be used in a lining according to FIG. 1, on an enlarged scale and in side elevation; and

FIG. 4 shows still another embodiment of a support assembly to be used in a lining according to FIG. 1, on an enlarged scale and in side elevation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a cross-sectional view of an underground excavation, showing a mine face 1, a mine filling or cavity 2, a mine floor 3 and a mine roof 4.

A conveyor 5 extending along the mine face 1, can be constructed, for instance, as a double scraper conveyor, and a mining machine 6 is guided on the conveyor 5 for displacement in relation thereto in the longitudinal direction of the same and comprises a driven cutter 7 for undercutting the mine face 1.

The lining according to the invention comprises a floor base 8 having two sides, one of which serves for supporting a shield 9 and the other one of which is free, and extends toward the mine face. The shield 9 is attached to the one side of the floor base so as to be pivotable in relation thereto, and comprises means for supporting a roof cap 10. A pit prop 11 engages the floor base 8 and the shield 9 and serves for adjustable support of the shield 9 and, consequently, of the roof cap 10 on the floor base 8.

It is to be understood that the invention is not limited to the illustrated and described number of the various elements of the lining. Rather, the lining can comprise two or more pit props l1, and the floor base 8 which is shown to have only one part can also comprise a plurality of parts. In a preferable embodiment of the invention, the arched shield 9 which extends over the floor base 8 comprises a plurality of trough-shaped rods which are mutually spaced so that the overall width of the shield 9 substantially corresponds to the width of the floor base 8, the flanges of these trough-shaped rods extending in the direction toward the cavity 2.

The drawing does not illustrate either the specific construction of the shield 9 as discussed above, or the means for displacement of the lining toward the mine face 1 after completion of one undercutting operation, since these features are not essential for the invention. In other words, any other conventional shield construction and any displacement means which are known to the expert in the field of mining can be used without affecting the scope of the invention. For instance, the lining may be operatively associated with the conveyor 5, possibly with interposition of a shifting cylinder.

It is evident from FIG. 1 when considered in conjunction with FIG. 2 that a free upper end of the shield 9 is provided with a bearing for accommodation of a pivot 12 supporting the roof cap 10 in the shield 9 for rotation in relation thereto, while the other lower end comprises a bearing for insertion therein of a pivot 13 which is an integral part of an adjustable support assembly 14 interposed between the shield 9 and the floor base 8.

In the embodiment of the invention as illustrated in FIGS. I and 2, the support assembly 14 comprises a support plate 15 whose lower end is mounted for rotation about a pivot 16 which is supported in bearing brackets 17 rigidly attached to the floor base 8. The width of the support plate 15 corresponds substantially to the width of the floor base 8 and of the shield 9. The pivot 13 serving for connection between the support plate 15 and the shield 9 is accommodated in holes provided at the upper end of the support plate 15 and en gages bearings of the shield 8. In this manner, the pivot 13 follows a circular path during the rotation of the pivoted support plate 15 about the lower pivot 16, so that the distance between the lower end of the shield 9 and the floor base increases as the support plate 15 is displaced from the one (in the drawing the right) side of the floor base 3 in the direction toward the position in which the support plate 15 is perpendicular to the floor base 8, Le. the distance of the lower end of the shield 9 from the mine floor 3 increases as the same is displaced toward the mine face 1. This movement of the lower end, in cooperation with the extension of the pit prop 11, results in a substantially vertical movement of the projecting end of the roof cap 10, so that the distance of this free end from the mine face 1 is kept virtually constant regardless of the instantaneous thickness of the seam being exploited.

FIGS. 1 and 2 also show that the support plate is bifurcated in the region of its upper end. This bifurcation serves two purposes. First of all, the lower end of the shield 9 is accommodated in recesses 18 and secured therein by the pivot 13 extending through bores provided in the support plate 15 and bearings in the lower end of the shield 9. Secondly, these recesses 18 are large enough for accommodation therein, and passage therethrough, of two adjusting levers 19. These adjusting levers 19 are pivoted about a pivot 20 which is supported at the one side of the floor base 8 facing the exploited cavity 2 so as to rotate in the vertical plane. FIG. 1 shows that the adjusting levers 19 are provided with bores 21. These bores 21 as well as bores 22 provided in brackets 23 which are welded or otherwise attached to the support plate 15 serve for accommodation of a detent 24. This arrangement renders possible the fixation of the support plate 15 in any position defined by the alignment of the bores 21 of the adjusting levers 19 with the bores 22 of the brackets 23. FIG. 1 shows an intermediate fixed position of the support assembly 14, in which the support plate 15 encloses an acute angle of approximately 45 with the one end of the floor base 8 facing the cavity 2. However, this angle can also be smaller, amounting to as little a approximately as well as larger, amounting to up to 90, in order to render possible the adjustment of the shield 9 and the roof cap 10 to the instantaneous seam thickness in such a manner that the projecting end of the cap 10 is as close to the mine face 1 as possible.

FIG. 3 shows a different embodiment of the support assembly 14, wherein the same numerals are used for the corresponding parts shown in FIGS. 1 and 2, with the difference that the adjusting levers 19 are provided with recesses 25 which are open in the direction toward the support plate 15 so as to accommodate the detent 2 of the support plate 15. Self-locking keys 26 serve for securing the detent 24 in the respectively selected recess 25.

A still further, and currently preferred, embodiment of the present invention is shown in FIG. 4, which differs from those shown in FIGS. 1 to 3 in that the support plate 15 is provided at its lower end with a cylindrical surface which is eccentric in relation to the axis of the pivot 16, and that the pivot 16 is accommodated in a cam opening of a bracket 27 so as to be displaceable in the vertical direction. It is achieved in this manner that the support plate is progressively lifted in the region of the pivot 16 while resting on its gradually increasing cylindrical surface, so that the support plate 15 not only rotates about the pivot 16, but also displaces the same in the vertical direction within the cam opening of the bracket 27 so that the path along which the pivot 13 connecting the supporting plate 15 to the shield 9 travels is determined by the superimposition of the rotational movement about the pivot 16 and the vertical movement of the pivot 16. The result of this movement even better complies with the requirement of keeping the distance between the projecting end of the roof cap 10 and the mine face 1 to a minimum, since the trajectory of the pivot 13 and thus the lower end of the shield 9 is steeper when compared with the circular trajectory achieved in the previous embodiments, and the compliance with the desired vertical movement of the projecting end of the roof cap 10 is even better.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions, differing from the types described above, both within and without the mining industry.

While the invention has been illustrated and described as embodied in a lining for underground excavations it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. In a lining for underground excavations, a combination comprising a floor base having two spaced sides; a shield comprising at least one part which extends over said floor base in direction from one toward the other of said sides and has a free end portion, and an other end portion spaced from said free end portion in said direction; a roof cap attached to said free end portion of said shield and projecting beyond the same; at least one pit prop arranged between and engaging said floor base and said shield and being extendable so as to adjustably support said shield and said roof cap on said floor base; a bracket attached to said floor base and provided with an elongated cam opening; and an adjustable support assembly comprising a first pivot supported in said cam opening for displacement longitudinally thereof, a support mounted for rotation about and displacement together with said first pivot relative to said floor base and having a floor base portion of an eccentric cylindrical configuration abutting against said floor base and subjecting said first pin to displacement longitudinally of said cam opening during the rotation of said support, a second pivot engaging said other end portion of said shield so as to subject said other end portion to displacement along an arcuate path extending in said direction and through a plurality of positions during the rotation of said support so that the distance of said other end portion from said floor base increases as said support rotates from said one to said other side due to the rotation of said support and displacement of said first pivot in said cam opening, and means for fixing said other end portion in selected positions of said plurality.

2. A lining according to claim 1, wherein said support is shaped as a support plate whose dimension in the axial direction of said pivots substantially corresponds to dimensions of said floor base and said shield in the same direction.

3. A lining according to claim 1, wherein said fixing means comprises at least one adjusting lever pivotably attached to said one side of said floor base and provided with a plurality of adjusting recesses which are spaced along said adjusting lever, and wherein a detent is accommodated in said support and in one recess of said plurality of recesses.

4. A lining according to claim 3, wherein said recesses of said adjusting lever are holes, and wherein said detent is inserted into said support and said holes.

5. A lining according to claim 3, wherein said recesses are open in direction toward said support, wherein said adjusting device comprises at least one self-locking key and accomodation means for the same on said adjusting lever, and wherein said detent inserted into one recess of said plurality of recesses is secured therein by said self-locking key.

6. A lining according to claim 1, wherein said plurality of positions of said support within said range includes a first position in which said support encloses an acute angle of 30 with said one side of said floor base, a second position in which said support is perpendicular to said floor base, and at least one intermediate position.

7. In a lining for underground excavations, a combination comprising a floor base having two spaced sides; a shield comprising at least one part which extends over said floor base in direction from one toward the other of said sides and has a free end portion, and an other end portion spaced from said free end portion in said direction; a roof cap attached to said free end portion of said shield and projecting beyond the same; at least one pit prop arranged between and engaging said floor base and said shield and being extendable so as to adjustably support said shield and said roof cap on said floor base; and an adjustable support assembly comprising a first pivot mounted on said floor base, a support mounted on said first pivot for rotation within a limited range in relation to said floor base, a second pivot connecting said support to said other end portion of said shield so that the latter is displaced along an arcuate path extending in said direction and through a plurality of positions during the rotation of said support so that the distance of said other end portion from said floor base increases as said support rotates from said one to said other side, and an adjusting device for fixing said other end portion in selected positions of said plurality and including at least one adjusting lever pivotably attached to said one side of said floor base and provided with a plurality of adjusting recesses spaced along said adjusting lever, and a detent accommodated in said support and in a selected one of said plurality of recesses.

8. A lining according to claim 7, wherein said support is shaped as a support plate whose dimension in the axial direction of said pivots substantially corresponds to dimensions of said floor base and said shield in the same direction.

9. A lining according to claim 7, wherein said recesses of said adjusting lever are holes, and wherein said detent is inserted into said support and said holes.

10. A lining according to claim 7, wherein said recesses are open in direction toward said support; wherein said adjusting device comprises at least one self-locking key and accomodation means for the same on said adjusting lever, and wherein said detent inserted into one recess of said plurality of recesses is secured therein by said self-locking key.

11. A lining according to claim 8, wherein said support plate is provided with recesses and wherein said assembly further comprises two adjusting levers carried by said floor base and adapted for engagement in said recesses, said support plate and said adjusting levers being adjustable in a plurality of positions relative to one another.

12. A lining according to claim 7, wherein said plurality of positions of said support within said range includes a first position in which said support encloses an acute angle of 30 with said one side of said floor base, a second position in which said support is perpendicular to said floor base, and at least one intermediate po sition.

13. A lining according to claim 7, wherein said support plate is provided with recesses and wherein said assembly further comprises two adjusting levers carried by said floor base and adapted for engagement in said recesses, said support plate and said adjusting levers being adjustable in a plurality of positions relative to one another.

14. A lining according to claim 7, wherein said support is mounted for rotation about and displacement together with said first pivot relative to said floor base, so that the vertical distance of said other end portion of said shield from said floor base increases as said support rotates from said one side to said other side due to rotation of said support and displacement of said first pivot.

15. A lining according to claim 14, wherein a bracket provided with a cam opening is attached to said floor base and said first pivot is accommodated is said cam opening, and wherein said support has a floor base portion of an eccentric cylindrical configuration, which abuts against said floor base so as to subject said first pin to displacement in said cam opening during the rotation of said support. 

1. In a lining for underground excavations, a combination comprising a floor base having two spaced sides; a shield comprising at least one part which extends over said floor base in direction from one toward the other of said sides and has a free end portion, and an other end portion spaced from said free end portion in said diRection; a roof cap attached to said free end portion of said shield and projecting beyond the same; at least one pit prop arranged between and engaging said floor base and said shield and being extendable so as to adjustably support said shield and said roof cap on said floor base; a bracket attached to said floor base and provided with an elongated cam opening; and an adjustable support assembly comprising a first pivot supported in said cam opening for displacement longitudinally thereof, a support mounted for rotation about and displacement together with said first pivot relative to said floor base and having a floor base portion of an eccentric cylindrical configuration abutting against said floor base and subjecting said first pin to displacement longitudinally of said cam opening during the rotation of said support, a second pivot engaging said other end portion of said shield so as to subject said other end portion to displacement along an arcuate path extending in said direction and through a plurality of positions during the rotation of said support so that the distance of said other end portion from said floor base increases as said support rotates from said one to said other side due to the rotation of said support and displacement of said first pivot in said cam opening, and means for fixing said other end portion in selected positions of said plurality.
 2. A lining according to claim 1, wherein said support is shaped as a support plate whose dimension in the axial direction of said pivots substantially corresponds to dimensions of said floor base and said shield in the same direction.
 3. A lining according to claim 1, wherein said fixing means comprises at least one adjusting lever pivotably attached to said one side of said floor base and provided with a plurality of adjusting recesses which are spaced along said adjusting lever, and wherein a detent is accommodated in said support and in one recess of said plurality of recesses.
 4. A lining according to claim 3, wherein said recesses of said adjusting lever are holes, and wherein said detent is inserted into said support and said holes.
 5. A lining according to claim 3, wherein said recesses are open in direction toward said support, wherein said adjusting device comprises at least one self-locking key and accomodation means for the same on said adjusting lever, and wherein said detent inserted into one recess of said plurality of recesses is secured therein by said self-locking key.
 6. A lining according to claim 1, wherein said plurality of positions of said support within said range includes a first position in which said support encloses an acute angle of 30* with said one side of said floor base, a second position in which said support is perpendicular to said floor base, and at least one intermediate position.
 7. In a lining for underground excavations, a combination comprising a floor base having two spaced sides; a shield comprising at least one part which extends over said floor base in direction from one toward the other of said sides and has a free end portion, and an other end portion spaced from said free end portion in said direction; a roof cap attached to said free end portion of said shield and projecting beyond the same; at least one pit prop arranged between and engaging said floor base and said shield and being extendable so as to adjustably support said shield and said roof cap on said floor base; and an adjustable support assembly comprising a first pivot mounted on said floor base, a support mounted on said first pivot for rotation within a limited range in relation to said floor base, a second pivot connecting said support to said other end portion of said shield so that the latter is displaced along an arcuate path extending in said direction and through a plurality of positions during the rotation of said support so that the distance of said other end portion from said floor base increases as said support rotates from said one To said other side, and an adjusting device for fixing said other end portion in selected positions of said plurality and including at least one adjusting lever pivotably attached to said one side of said floor base and provided with a plurality of adjusting recesses spaced along said adjusting lever, and a detent accommodated in said support and in a selected one of said plurality of recesses.
 8. A lining according to claim 7, wherein said support is shaped as a support plate whose dimension in the axial direction of said pivots substantially corresponds to dimensions of said floor base and said shield in the same direction.
 9. A lining according to claim 7, wherein said recesses of said adjusting lever are holes, and wherein said detent is inserted into said support and said holes.
 10. A lining according to claim 7, wherein said recesses are open in direction toward said support; wherein said adjusting device comprises at least one self-locking key and accomodation means for the same on said adjusting lever, and wherein said detent inserted into one recess of said plurality of recesses is secured therein by said self-locking key.
 11. A lining according to claim 8, wherein said support plate is provided with recesses and wherein said assembly further comprises two adjusting levers carried by said floor base and adapted for engagement in said recesses, said support plate and said adjusting levers being adjustable in a plurality of positions relative to one another.
 12. A lining according to claim 7, wherein said plurality of positions of said support within said range includes a first position in which said support encloses an acute angle of 30* with said one side of said floor base, a second position in which said support is perpendicular to said floor base, and at least one intermediate position.
 13. A lining according to claim 7, wherein said support plate is provided with recesses and wherein said assembly further comprises two adjusting levers carried by said floor base and adapted for engagement in said recesses, said support plate and said adjusting levers being adjustable in a plurality of positions relative to one another.
 14. A lining according to claim 7, wherein said support is mounted for rotation about and displacement together with said first pivot relative to said floor base, so that the vertical distance of said other end portion of said shield from said floor base increases as said support rotates from said one side to said other side due to rotation of said support and displacement of said first pivot.
 15. A lining according to claim 14, wherein a bracket provided with a cam opening is attached to said floor base and said first pivot is accommodated is said cam opening, and wherein said support has a floor base portion of an eccentric cylindrical configuration, which abuts against said floor base so as to subject said first pin to displacement in said cam opening during the rotation of said support. 